Interview Questions and Answers for 'Exception' | Search Interview Question

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Q31. Difference between Error and Exception ?

Ans. An Error indicates serious problems that a reasonable application should not try to catch whereas

An Exception indicates conditions that a reasonable application might want to catch.

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Q32. What is Java NumberFormatException ?

Core Java

Ans. NumberFormatException is the exception that Java throws when we try to convert one data type to the Number data type but the value is not parsable to be a Number.

For example , the following code will result in the NumberFormatException

String string = "Buggy";
int strtoInt = Integer.parseInt(string);

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Q33. How can we catch an exception thrown by another thread ?

Core Java

Ans. http://stackoverflow.com/a/6548203/2789764

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Frequently asked.

Q34. When does the finally block gets executed ?

Core Java

Ans. A finally block of code always executes, whether or not an exception has occurred.The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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Q35. Can we have try statement without catch? If try statement contains return will the finally block be executed? What happens if there is an exception inside finally block?

Core Java

Ans. Yes, with finally.

Yes, finally block will be executed even if there is no exception in try block.

If finally throws an exception, the exception gets thrown to the calling module.

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Q36. Explain Exception Hierarchy in Java SE ?

Core Java

Ans. <a href="http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/" rel="nofollow">http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/</a>

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Q37. What happens to the Exception object after the exception handling is done ?

Core Java

Ans. As with all other objects its garbage collected after its usage unless its rethrown.

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Q38. What are the fail safe systems ?

Operating System

Ans. Fail Safe systems are tolerant systems that continue processing even if they sense any problem. the objective here is to continue with the processing even if there are some problems instead of completely shutting it down. Example could be to catch an exception and still letting it complete with partial results.

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Frequently asked at HCL Technologies ( Based on 3 feedback )

Q39. Difference between Checked and Unchecked exceptions ?

Core Java

Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.

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Q40. How does a try statement determine which catch clause should be used to handle an exception?

Core Java

Ans. When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored.

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Q41. Give an Example of checked and unchecked exception ?

Core Java

Ans. ClassNotFoundException is checked exception whereas NoClassDefFoundError is a unchecked exception.

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Q42. Name few Java Exceptions ?

Core Java

Ans. IndexOutofBoundException ,
NoClassDefFoundException ,
OutOfMemoryException ,
IllegalArgumentException,
NullPointerException,
IllegalStateException

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Q43. How can we make sure that a code segment gets executed even in case of uncatched exceptions ?

Ans. By putting it within finally.

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Q44. Explain java.lang.OutOfMemoryError ?

Core Java

Ans. This Error is thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.

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Q45. Is it necessary that each try block to be followed by catch block ?

Core Java

Ans. It should be followed by either catch or finally block.

Sample Code for Retry in case of exception

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Q46. Can finally block be used without catch ?

Core Java

Ans. Yes but should follow "try" block then.

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Q47. What is exception propogation ?

Core Java

Ans. Passing the exception object to the calling method.

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Q48. When do you get ClassCastException?

or

What is ClassCastException ?

Ans. As we only downcast class in the hierarchy, The ClassCastException is thrown to indicate that code has attempted to cast an object to a subclass of which it is not an instance.

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Q49. How would you go about debugging a NullPointerException?

Core Java

Ans. Open ended Questions.

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Q50. How compiler handles the exceptions in overriding ?

Core Java

Ans. 1)The overriding methods can throw any runtime Exception , here in the case of runtime exception overriding method (subclass method) should not worry about exception being thrown by superclass method.

2)If superclass method does not throw any exception then while overriding, the subclass method can not throw any new checked exception but it can throw any runtime exception

3) Different exceptions in java follow some hierarchy tree(inheritance). In this case , if superclass method throws any checked exception , then while overriding the method in subclass we can not throw any new checked exception or any checked exception which are higher in hierarchy than the exception thrown in superclass method

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Q51. Difference between throw and throws ?

Core Java

Ans. throw is used to explicitly throw an exception especially custom exceptions, whereas throws is used to declare that the method can throw an exception.

We cannot throw multiple exceptions using throw statement but we can declare that a method can throw multiple exceptions using throws and comma separator.

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Q52. What are the sub classes of Exception class?

Core Java

Ans. The Exception class has two main subclasses : IOException class and RuntimeException Class.

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Q53. How finally used under Exception Handling?

Core Java

Ans. The finally keyword is used to create a block of code that follows a try block. A finally block of code always executes, whether or not an exception has occurred.

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Q54. What things should be kept in mind while creating your own exceptions in Java?

Core Java

Ans. All exceptions must be a child of Throwable.

If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.

You want to write a runtime exception, you need to extend the RuntimeException class.

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Q55. Can try statements be nested?

Core Java

Ans. Yes

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Q56. Will finally be called always if all code has been kept in try block ?

Core Java

Ans. The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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Q57. what will be the output ?

class Animal {
public void eat() throws Exception {
}
}

class Dog2 extends Animal {
public void eat(){}
public static void main(){
Animal an = new Dog2();
an.eat();
}
}

Core Java

Ans. Compile Time Error: Unhandled exception type Exception

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Q58. Can finally block throw an exception ?

Core Java

Ans. Yes. Methods invoked from within a finally block can throw an exception. Failure to catch and handle such exceptions results in the abrupt termination of the entire try block.

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Q59. Can we have try and catch blocks within finally ?

Core Java

Ans. Yes, if we have a cleanup code that might throw an exception in the finally block, then we can have a try-catch block

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Q60. Which exception should be handled in the following code ?

File file = new File("../file.txt");
FileWriter fileWriter = new FileWriter(file);

Core Java

Ans. IOException

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